I propose to monitor, on a structural basis, the regulation of glycogen synthase by phosphorylation-dephosphorylation reactions. The roles of cyclic-AMP-dependent and -independent protein kinases in this process will be assessed by studying cultured mammalian cells that have lost cyclic-AMP-dependent kinase activity by mutation. The methods to be used include labelling the synthase with 32P in intact cells, purification of the enzyme by immunological methods, cleavage of the 32P-synthase into small peptides, resolving the peptides, and determining the 32P content of these peptides. These methods will also be applied to tissue from animal models of human insulin "resistance". It should be possible to determine if dephosphorylations promoted by insulin in control tissue still occur in tissue from insulin-resistant animals. In addition, these methods can establish if insulin "resistance" involves phosphorylations of glycogen synthase at sites not phosphorylated on the enzyme from control tissue. Ultimately, application of such methods to human tissue may disclose if an alteration in the phosphorylation state of glycogen synthase is part of the biochemical basis of insulin "resistance" associated with maturity-onset diabetes and obesity.